[MARTINSR]

There isn't much to think about, you welded that end on crooked. There is a possibility it could have been welded too hot on the right side at the trunk and it shrunk while cooling bringing it in at the back as MP&C suggests. But damn that would have taken a lot of heat in the gutter all at once without anything being welded out on the outside at the top corner at all, I honestly don't think it's very possible.

It's more about it being crooked when it was welded.

I see that the trunk was on there while you were fitting it, but was it checked a LOT as the job progressed?

Trial fitting parts like that tail light/quarter extension and all is a MUST while the work progresses.

And of course the right way to repair this is cut the thing off along the top and move it over straightening it out like it should be.

Brian